DESCRIPTION (applicant's abstract): It is well established that steroid hormones (e.g., estradiol) can regulate stereotypic reproductive behaviors (e.g., lordosis) in potentially hazardous pest species by regulating the sensitivity of their pheromone detection system to chemosensory stimuli. However, previous studies have focused mainly on the central components of the pheromone system, i.e., regions within the central nervous system. Although there is compelling indirect evidence that estradiol can modulate neuronal activity of the vomeronasal organ (VNO), which is the epithelial component of this system, there remains little biochemical support for this effect. The long-term objective of this study is to understand the genetic basis of estradiol-dependent activational effects on the mammalian VNO. Within this context, the proposed work will characterize several features of estradiol-mediated gene expression and physiological effects in female rat VNO sensory neurons. Its specific aims are: 1) To determine if estradiol can activate gene expression in VNO sensory neurons and influence sensory neuron response to male pheromones; 2) To determine if estradiol can influence signal transduction in VNO neurons by correlating patterns of estrogen receptor expression with the expression patterns of critical components of the pheromone transduction pathway; and 3) To isolate and characterize a repertoire of putative estradiol-inducible genes expressed in the VNO neuroepithelium, Thus, this work will provide significant insight into the effects of steroid hormones on pheromone-mediated reproductive behaviors by providing the first direct evidence that estradiol can influence pheromonal processing at the level of the VNO. Furthermore, by clarifying the mechanisms underlying endocrine control of reproductive behaviors in a rodent pest species, this work will be particularly relevant to issues of public health.